The present invention relates to an optical communication or modulation device. In particular, the present invention relates to an optical communication device in which information borne by a first beam of photons is controllably passed to a second beam of photons that is thence distributed to a set of photon receptor elements. Further, the present invention relates to spectral information in the second beam of photons that is diffracted into multiple parts by surface plasmons to provide spatial separation of different wavelengths in the second beam of photons. Further, the invention relates to amplification of an optical communication signal.
Photon signal processing has an increasing importance in telecommunications and data processing. In optical communication systems, it is often necessary to analyze, energy-amplify, process, or distribute photon signals that are particularly brief or rapidly changing. In such systems, it is desirable to minimize processing and distribution time. It is also desirable to spatially separate and distribute information content in a rapid and controllably varying manner. In many applications, processing or distribution elements of an optical communication system should provide response times of the order of femtoseconds, and have passbands extending up into the petahertz range. Fiber optic transmission networks which incorporate opto-electronic, electro-optic, opto-mechanical, or other devices involving physical electronics or electrodes have response times that are generally too slow and passbands that are generally too narrow.
What is needed, therefore, is a system having a faster response time and broader bandwidth than is currently available for modulating, amplifying, and/or distributing brief and rapidly varying photon signals.
The above and other needs are met by an optical communication device having a first photon source, such as an infrared laser, for providing a first beam of photons modulated with information. The device includes an intersection plane for intersecting the first beam of photons at a first angle of incidence and for reflecting a first portion of the first beam of photons to form a reflected beam of photons propagating at a second angle of incidence. A polarization rotating structure is provided to rotate the polarization of the reflected beam of photons. A reflecting structure reflects the reflected beam of photons to form a second beam of photons. The second beam is passed through the polarization rotating structure to rotate the polarization of the second beam of photons. The intersection plane receives the second beam of photons at the second incidence angle, and intersects the second beam of photons with the first beam of photons. In a most preferred embodiment of the invention, a film layer at the intersection plane supports a first surface plasmon wave formed by the first beam of photons and a second surface plasmon wave formed by the second beam of photons. Interaction between the first and second surface plasmon waves on the film layer forms a surface plasmon standing wave. A second photon source, such as an ultraviolet laser, provides a third beam of photons which passes through the film layer at the intersection of the first and second beams of photons. As the third beam of photons passes through the film layer, the surface plasmon standing wave modulates the third beam with the information carried by the first beam.
Also in a preferred embodiment, the surface plasmon standing wave on the film layer is operable to scatter the third beam of photons in a diffraction pattern having a central peak portion and side peak portions spatially disposed on either side of the central peak portion. Some preferred embodiments include a first photon collection device, such as a photodetector, which is operable to receive the first peak portion, and at least one second photon collection device operable to receive at least one of the side peak portions.
In an alternative embodiment, the invention provides an optical communication device that includes a first photon source, such as a laser, for emitting a first beam of photons in a first direction, where the first beam of photons is modulated with information. A beam splitter receives the first beam and divides the first beam into second and third beams of photons. A beam directing structure directs the second beam in a second direction, and directs the third beam in a third direction which is different from the second direction. The second and third beams intersect at an intersection plane, there being a second incidence angle between the second beam and the intersection plane, and a third incidence angle between the third beam and the intersection plane. The device has a second photon source, such as a laser, for emitting a fourth beam of photons that intersects the second and third beams at the intersection plane. The device further includes a film layer, such as a metal film, disposed at the intersection plane which is transmissive to the fourth beam of photons. Based on interaction between the second, third, and fourth beams on the film layer, the fourth beam is modulated with the information as the fourth beam passes through the film layer.
In another aspect, the invention provides a method for modulating a carrier beam of photons with information carried by a first beam of photons. The method includes steps of propagating a first beam of photons in a first direction, and reflecting a portion of the first beam to form a reflected beam propagating in a second direction. The reflected beam is reflected to form a second beam which is substantially collinear with the reflected beam and which propagates in a third direction opposite the second direction. The polarization of the second beam is rotated, and the second beam is intersected with the first beam at an intersection plane. The method further includes propagating a carrier beam of photons toward the intersection plane, and intersecting the carrier beam with the first and second beams at the intersection plane. Based on interactions between the first, second, and carrier beams at the intersection plane, the carrier beam is modulated with the information as the carrier beam passes through the intersection plane.